Zhongguo shipin weisheng zazhi (Jan 2022)
Study of association between deletion of key virulence genes and pathogenicity of Listeria monocytogenes in Chaoyang District of Beijing
Abstract
ObjectiveTo investigate the association between deletion of key virulence genes and pathogenicity and serotype of 81 strains of Listeria monocytogenes(L.monocytogens) isolates in Chaoyang district of Beijing from 2016-2018.MethodsSerotyping was performed on 81 strains of L. monocytogenes by polymerase chain reaction (PCR) and serum agglutination assay, and 11 virulence genes (inlA, inlC, inlJ, plcB, prfA, mpl, iap, hly, actA, inlB, plcA) were detected by PCR. The susceptibility of these strains to 9 antibiotics were tested by broth dilution. Based on the epidemiological survey data, the relationship between the deletion of key virulence genes, pathogenicity and serotype of L. monocytogenes was studied.ResultsThe 81 strains of L. monocytogenes were classified into 4 serotypes: 1/2a serotype 50.62% (41/81), 1/2b serotype 29.63% (24/81), 1/2c serotype 11.11% (9/81) and 4b serotype 8.64% (7/81). The predominant serotype of food isolates and patient isolates were 1/2a. The positive rates of virulence genes inlA, inlC, inlJ, plcB, prfA and mpl were 100%. The positive rates of iap, hly, actA, inlB and plcA were 98.77%, 98.77%, 97.53%, 80.25% and 38.27% respectively. The proportions of the 81 strains of L. monocytogenes carrying 7, 8, 9, 10 and 11 virulence genes were 1.23% (1/81), 2.47% (2/81), 7.41% (6/81), 59.26% (48/81) and 29.63% (24/81). The positive rate of hly in genotype 1/2c was lower than that in other serotypes, and plcA was only 100% carried in genotype 1/2b and 4b. 70.37% (57/81) isolates lacked 11 virulence genes and 1/2a (41/57, 71.93%) was the main serotype. Only inlB was not detected in 1/2b (6/24, 25.00%) and 4b (1/7, 14.29%) serotype. There was no significant difference in the distribution of gender, age, pregnancy related or not, and the source of strains in 16 virulence gene deletion strains isolated from patients (P>0.05). The resistant rates of 81 strains of L. monocytogenes to penicillin, erythromycin and ampicillin were 4.94%. MIC to chloramphenicol of 57 strains was as high as 16 μg/mL and MIC to the other antibiotics was low. There were three drug-resistant strains in the virulence gene deletion strains, and one inlB deletion strain was resistant to penicillin, erythromycin and ampicillin. Another inlB deletion strain was resistant to penicillin. The plcA deletion strain was resistant to erythromycin.ConclusionThe dominant serotypes of L. monocytogenes isolated from food and patients in Chaoyang district of Beijing was 1/2a. There were some virulence gene deletion strains. Deletion of some virulence genes had limited effect on pathogenicity of L. monocytogenes strains. The drug resistance rate of L. monocytogenes isolated from food and clinic was low, but surveillance and control of virulence genes and drug resistance of L. monocytogenes should be strengthened.
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